Diamond

A diamond is a crystal made up entirely of carbon atoms that are arranged in an isometric, or cubic, matrix. A cubic crystal arrangement is one in which the crystal essentially expands outward at the same rate in all directions during its initial growth; the ideal result, when the crystal forms without any interference, is a pure and perfectly formed octahedral shape.

The unique characteristics of diamond go far beyond what you can see with your eye. In addition to their superior brilliance and dispersion, diamonds are the hardest natural substance on earth.

Diamond rates a 10 on the Mohs scale of hardness, which means that it is extremely resistant to scratches; it is several times harder than the next-hardest substance, corundum, which is more commonly known as ruby and sapphire.

Silver

Fine Silver in its natural state, 999/1000 pure, is too soft an element for practical jewelry. To make it workable, an alloy such as copper is added. Here are the main silver alloys:

Sterling Silver: A mixture of 92.5 % pure silver (925 parts) and 7.5 % metal alloy.

Silver Plating: Also known as silver plated or silver coated. A base metal, usually nickel silver or brass, is coated with a layer of pure silver by a process called electroplating.

Vermeil: Sterling silver electroplated with at least 100 millionths of an inch of karat gold

German Silver or Nickel Silver: A silver-white alloy consisting of copper, zinc and nickel.

Coin Silver: 90% (900 parts) pure silver and 10% (100 parts) metal alloy. A process of melting down coins done in the 19th century, and mostly discarded today.

Gold

Gold's purity is measured in karats. The term "karat" harks back to the ancient bazaars where "carob" beans were used to weigh precious metals. 24 karat is pure gold, but its purity means it is more expensive and less durable than gold that is alloyed with other metals. Different alloys are used in jewelry for greater strength, durability and color range.

The karatage of the jewelry will tell you what percentage of gold it contains: 24 karat is 100 percent, 18 karat is 75 percent, and 14 karat is 58 percent gold. When comparing gold jewelry, the higher the number of karats, the greater the value.

Platinum

The appeal of platinum is in its appearance. Its white luster is unique. It is also the strongest precious metal used in jewelry, and is almost twice as heavy as 14-karat gold. This weight is one of platinum's strongest selling points, because it gives "heft" to fine jewelry, which people naturally equate with value.